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Title: Selective Electrocatalytic Reduction of CO2 into CO at Small, Thiol-Capped Au/Cu Nanoparticles

Abstract

The electrochemical CO2 reduction reaction (CO2RR) is a promising approach for converting fossil fuel emissions into environmentally sustainable chemicals and fuels. The ability to control the surface structure of CO2RR nanocatalysts provides an opportunity to tune product selectivity. Bimetallic gold–copper catalysts have been identified as emerging electrocatalyst candidates, but Cu incorporation typically lowers product selectivity compared with pure Au. Here we show sustained CO selectivity and activity up to 49% Cu content in small (<2 nm), thiol-capped Au/Cu nanoparticles (NPs). Bimetallic NPs containing 49% Cu selectivity converted CO2 into CO with 100 ± 6% CO Faradaic efficiency and average mass activity of ~500 mA/mg during a 12 h electrolysis experiment at –0.8 V vs RHE. Au/Cu NPs synthesized without thiol ligands selectively produced H2, whereas larger (>10 nm), thermally dethiolated Au/Cu NPs produced a wider product distribution including H2, CO, and C2H4. Density functional theory (DFT) modeling of CO2RR and H2 evolution at realistic, thiol-capped Au/Cu NP structures indicated that copper–thiol surface structures sustained CO selectivity by stabilizing key *CO intermediates while making *H binding less favorable. Calculations also predicted that removing a significant fraction of the thiol ligands would increase *CO binding strength such that desorption of CO productmore » molecules could become the most thermodynamically challenging step. This result, coupled with increased *H stability on dethiolated nanoclusters, points to decreased CO2RR selectivity for small, ligand-free catalysts, which is in line with experimental observations from our group and others. Here, our results demonstrate that thiol-ligand surface structures can sustain the CO selectivity of bimetallic Au/Cu NPs and reduce precious metal requirements for CO2RR.« less

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2];  [2];  [2];  [2];  [1];  [2];  [1];  [1];  [1];  [3];  [4]; ORCiD logo [5]
  1. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)
  2. National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); AECOM, South Park, PA (United States)
  3. Louisiana State Univ., Baton Rouge, LA (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  5. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1477176
Report Number(s):
NETL-PUB-22320
Journal ID: ISSN 1932-7447
Grant/Contract Number:  
AC02-76SF00515; FE0004000; SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 49; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Kauffman, Douglas R., Alfonso, Dominic R., Tafen, De Nyago, Wang, Congjun, Zhou, Yunyun, Yu, Yang, Lekse, Jonathan W., Deng, Xingyi, Espinoza, Vanessa, Trindell, Jamie, Ranasingha, Oshadha K., Roy, Amitava, Lee, Jun -Sik, and Xin, Huolin L. Selective Electrocatalytic Reduction of CO2 into CO at Small, Thiol-Capped Au/Cu Nanoparticles. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.8b06234.
Kauffman, Douglas R., Alfonso, Dominic R., Tafen, De Nyago, Wang, Congjun, Zhou, Yunyun, Yu, Yang, Lekse, Jonathan W., Deng, Xingyi, Espinoza, Vanessa, Trindell, Jamie, Ranasingha, Oshadha K., Roy, Amitava, Lee, Jun -Sik, & Xin, Huolin L. Selective Electrocatalytic Reduction of CO2 into CO at Small, Thiol-Capped Au/Cu Nanoparticles. United States. https://doi.org/10.1021/acs.jpcc.8b06234
Kauffman, Douglas R., Alfonso, Dominic R., Tafen, De Nyago, Wang, Congjun, Zhou, Yunyun, Yu, Yang, Lekse, Jonathan W., Deng, Xingyi, Espinoza, Vanessa, Trindell, Jamie, Ranasingha, Oshadha K., Roy, Amitava, Lee, Jun -Sik, and Xin, Huolin L. 2018. "Selective Electrocatalytic Reduction of CO2 into CO at Small, Thiol-Capped Au/Cu Nanoparticles". United States. https://doi.org/10.1021/acs.jpcc.8b06234. https://www.osti.gov/servlets/purl/1477176.
@article{osti_1477176,
title = {Selective Electrocatalytic Reduction of CO2 into CO at Small, Thiol-Capped Au/Cu Nanoparticles},
author = {Kauffman, Douglas R. and Alfonso, Dominic R. and Tafen, De Nyago and Wang, Congjun and Zhou, Yunyun and Yu, Yang and Lekse, Jonathan W. and Deng, Xingyi and Espinoza, Vanessa and Trindell, Jamie and Ranasingha, Oshadha K. and Roy, Amitava and Lee, Jun -Sik and Xin, Huolin L.},
abstractNote = {The electrochemical CO2 reduction reaction (CO2RR) is a promising approach for converting fossil fuel emissions into environmentally sustainable chemicals and fuels. The ability to control the surface structure of CO2RR nanocatalysts provides an opportunity to tune product selectivity. Bimetallic gold–copper catalysts have been identified as emerging electrocatalyst candidates, but Cu incorporation typically lowers product selectivity compared with pure Au. Here we show sustained CO selectivity and activity up to 49% Cu content in small (<2 nm), thiol-capped Au/Cu nanoparticles (NPs). Bimetallic NPs containing 49% Cu selectivity converted CO2 into CO with 100 ± 6% CO Faradaic efficiency and average mass activity of ~500 mA/mg during a 12 h electrolysis experiment at –0.8 V vs RHE. Au/Cu NPs synthesized without thiol ligands selectively produced H2, whereas larger (>10 nm), thermally dethiolated Au/Cu NPs produced a wider product distribution including H2, CO, and C2H4. Density functional theory (DFT) modeling of CO2RR and H2 evolution at realistic, thiol-capped Au/Cu NP structures indicated that copper–thiol surface structures sustained CO selectivity by stabilizing key *CO intermediates while making *H binding less favorable. Calculations also predicted that removing a significant fraction of the thiol ligands would increase *CO binding strength such that desorption of CO product molecules could become the most thermodynamically challenging step. This result, coupled with increased *H stability on dethiolated nanoclusters, points to decreased CO2RR selectivity for small, ligand-free catalysts, which is in line with experimental observations from our group and others. Here, our results demonstrate that thiol-ligand surface structures can sustain the CO selectivity of bimetallic Au/Cu NPs and reduce precious metal requirements for CO2RR.},
doi = {10.1021/acs.jpcc.8b06234},
url = {https://www.osti.gov/biblio/1477176}, journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 49,
volume = 122,
place = {United States},
year = {2018},
month = {8}
}

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